fix(macos): name the gateway instead of addressing it, so bottles survive it moving

The shared gateway's address is DHCP-assigned and changes whenever the infra
container is recreated — a source-hash bump, an image upgrade, a crash. Every
agent-facing URL embedded that address, and the proxy URL reaches the agent
as process environment at `container exec` time. A running process's environ
cannot be rewritten from outside, so a moved gateway stranded every running
bottle permanently: not degraded, unreachable, until relaunched and its agent
session thrown away.

Give the agent a stable name instead. `GATEWAY_HOSTNAME` replaces the address
in the egress proxy URL, NO_PROXY, git-http, and supervise URLs, and resolves
through the bottle's own /etc/hosts. Unlike environ that is a file, so it can
be rewritten inside a container that is already running — which is the whole
point: a gateway that returns at a new address is picked up by live bottles.

Launch writes the entry before anything execs (every agent URL names the
gateway, so it must resolve for the first connection), and re-points every
running bottle once the gateway is up, so one stranded by an earlier restart
re-attaches instead of needing a relaunch.

The write needs root and the agent runs as `node`: the host can repoint a
bottle's gateway name, the agent cannot repoint its own. Keep that asymmetry.

Apple Container 1.0 has no container-name DNS on a user network and
`container run` has no --add-host, so the entry is written by exec after
start rather than declared at run.

Does not address the other half of #443: per-bottle egress auth tokens are
held in memory by the orchestrator and are still lost across a restart, so a
re-attached bottle resolves its policy but not its injected credentials.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

bot_bottle/backend/macos_container/enumerate.py

@@ -8,7 +8,11 @@ from ...bottle_state import read_metadata
 from .. import ActiveAgent
 from .infra import INFRA_NAME
 
-_PREFIX = "bot-bottle-"
+# The name every agent container carries: `bot-bottle-<slug>`. Exported
+# because callers that act on a running bottle (gateway-host rewrites,
+# registry reconciliation) have to map an enumerated slug back to a
+# container name.
+CONTAINER_NAME_PREFIX = "bot-bottle-"
 # The shared per-host infra container carries the same prefix as agent
 # containers but is infrastructure, not a bottle — one control plane + gateway
 # serves every agent, so listing it as an agent would invent one per host.
@@ -26,9 +30,9 @@ def enumerate_active() -> list[ActiveAgent]:
         return []
     out: list[ActiveAgent] = []
     for name in sorted(line.strip() for line in result.stdout.splitlines()):
-        if not name.startswith(_PREFIX) or name in _INFRA_NAMES:
+        if not name.startswith(CONTAINER_NAME_PREFIX) or name in _INFRA_NAMES:
             continue
-        slug = name[len(_PREFIX):]
+        slug = name[len(CONTAINER_NAME_PREFIX):]
         metadata = read_metadata(slug)
         out.append(ActiveAgent(
             backend_name="macos-container",